Subjects received intravenous (IV) GLP-1 for one hour on one occasion. Endogenous insulin was released from the pancreas in response to the IV GLP-1. Blood levels were taken every 5 minutes and stored so that insulin levels could be measured. Glucose was infused via IV during that hour, so that the blood level of glucose was maintained at 90 mg/dl, which is euglycemic. For the hour following the GLP-1 infusion, samples were also taken every 5 minutes so that the blood glucose could be maintained at 90 mg/dl, and also so that the insulin could be measured. On a separate occasion, subjects received IV insulin to mimic the amount of insulin that was released by GLP-1 on the first study. We could then measure glucose uptake in both studies. If there is an alteration of the glucose uptake in Study 1 referable to Study 2, then the difference would have to be due to the fact that GLP-1 was given in Study 1.